This proposal is to bring together in one book on the history of neurophysiology a number of studies already begun by the applicant and to expand and add to them by further research. The plan is to trace a connecting theme based on the growth of philosophical ideas about the nervous system that led to experimentation during the 17th, 18th and 19th centuries. The documentation of this experimentation is one of the major features of this work for the impact of this development not only on the basic sciences of the nervous system but on the clinical understanding and treatment of neurological diseases is the essential drive of research in this field.